Ab initio study of the structure, stability, and vibrational spectra of chlorine and argon fluoride and oxide molecules and ions

Ab initio calculations of the potential energy surfaces (PESs) in the vicin ity of equilibrium structures of chlorine fluoride and oxide molecules and ions ClF2+/-, ClO2+/-, ClF3, ClO3+/-, ClF4+/-, ClO4-, ClF5, ClF6+/-, and Cl F7 and similar hypothetical argon molecules and ions with closed electron s hells were performed at the Hartree-Fock (HF) and correlated (MP2) levels o f theory using 6-31(+)G* and 6-311(+)G* basis sets. The equilibrium geometr y parameters and frequencies and intensities of normal vibrations were dete rmined, and the energies of decomposition with the elimination of the fluor ide F- ion and the F-2 molecule were estimated. The effect of electron corr elation on the results of calculations was studied. The trends in the behav ior of molecular properties in various series of fluorides and oxides were followed, and the properties of unknown compounds were predicted. Local min ima lying considerably higher than the dissociation limit were found on the PESs of the fluoride cations, ArF3+ (C-2v) and ArF5+ (C-4v), and dications , ArF22+ (C-2v), ArF42+ (C-4v), and ArF62+ (O-h), and the ArO4 (T-d) tetrox ide at both the HF and MP2 levels of theory. By structural and vibrational parameters, the configurations corresponding to these minima are only sligh tly different from those of the isoelectronic chlorine fluorides ClF3, ClF5 , ClF2+, ClF4+, and ClF6+ and the perchlorate ion. A similar local minimum was localized on the PES of chlorine heptafluoride ClF7 (D-5h). It was supp osed that ClF7 and some of the above argon compounds can occur as metastabl e intermediates.